A ground-based program for exobiological experiments on the International Space Station

The International Space Station will carry the external facility EXPOSE for exobiological studies under free space conditions and/or selected space parameters. Complementary to such experimentation in space, a profound ground support program under simulated space conditions is required: (i) to support the scientific EXPOSE community in the definition of the experiments under simulated space conditions; (ii) to determine the compatibility of the different experiments (e.g., organics and biology); (iii) to optimize the experiments; (iv) to perform experiments sequence tests under simulated EXPOSE environment conditions; (v) to run ground controls in parallel to the mission; and (vi) for postflight analysis of phenomena observed in space. For these laboratory studies, testbeds are available at DLR and GSF that simulate the parameters of space, such as vacuum, solar electromagnetic and cosmic ionizing radiation, temperature extremes and reduced gravity that can be applied separately, or in selected combinations. Such studies contribute to answer several questions pertinent to exobiology, such as the relevance of the delivery of extraterrestrial organic molecules to the Earth for the origin of life, the role of solar UV radiation in genetic stability, strategies of adaptation to environmental extremes, the probability and limits for interplanetary transfer of life, and the needs for planetary protection. (C) 2000 Elsevier Science Ltd. All rights reserved.